Telephone system



July 14, 1931. H. M. FRlENDLY TELEPHONE SYSTEM Q 1 Sheets-Sheet 1 Original Filed June '29, 1921 July 14, 1931. H. M. FRIENDLY TELEPHONE SYSTEM Origihal Filed June 29, 1921 10 Sheets-Sheet 2 July 14, 1931.

H. M. FRIENDLY TELEPHONE SYSTEM Original Filed June 29, 1921 10 Sheets-Sheet 5 RM Ohm CUE n July 14, 1931.

H. M. FRIENDLY TELEPHQNE SYSTEM Qriginal Filed June 29, 1921 10 Sheets-Sheet 4 July 14, 1931. H, M, FRIENDLY 1,814,794-

TELEPHONE SYSTEM v Original Filed June 2.9, 1921 10 Sheets-Sheet 5 Inverfiur- Herbert-MPH E11 1311;

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July 14, 1931.' H. M. FRIENDLY TELEPHONE SYSTEM Original Filed June 29 1921 10 Sheets-Sheet 6 July 14, 1931. H. M'..FRIEI\ ID LY TELEPHONE SYSTEM '10 Sheets-Sheet 8 Original Filed June 29, 1921 i3 v WNQ f .PQ l l H MM: \a MS [g I |.1l A, a QM Rfi oN QT Q IL Q SQ 3x 3 H D Em mm Internal- Herb ern-P'TFlen WY Aims July 14,1931. H. M. FRIENDLY TELEPHONE SYSTEM Original Filed June 29, 1921 10 Sheets-Sheet 9 P3 SQ 1 m3 9Q Q Inveninr- HarberrFPfiiendl l M tn Q noo 0 7 V m Ma N3 mnm mum Rm 0 1| ielil lfflf ILIIIIIVAJ 1| Ma w R 0 mg 3 wwm o o p j q o WNQ z w P 954: .l Pj

July 14, 1931. H. M. FRIENDLY 1,814,794

' TELEPHONE SYSTEM Original Filed June 29, 1921 10 Sheets-Sheet 10 O 0 O o. of

Inventnr- HBrhErH' I-fimnd subscribers Patented July 14, 1931 UNl l E D STATES PATENT. I

HERBERT IvI. ER N DL S I, 0E PORTLAND, OREGON; MILTON s. FRIENDLY ANUCENTEAIL 'rrws'r COMPANY OF ILLINOIS, EXEoUToEs 0E SAID. HERBERT-M. FRIENDLY, {DE-1 'cEAsEI) TELEPHONE SYSTEM Application filed June 29, 1921, Serial No. 481,259 Renewed march 9,1927.

called two wire common battery automatic telephone system fashas'been widely used, the present invention necessitatingnovel departures from equipments" heretofore known; in

: attaining'the' new objects; while" retaining 15 certain operative functions which are known. The exampled form o'f-th'e present invention, chosen to illustrate it gco'ntemplatesits adaptation to a eompr'ehensive five-digit automatic tele'ph' ne exchange systemconsisting il' 20 of main. branchotfice'sand 'a subpflice of one of the niain-ln'anch-offices. It li'asifor its objects the following an dother novelobjectsl a, Toprovide novel dual functioning switch ina' i'ibof'fice primarily seizable by a erininating' line-switch (also termed a pieselec'tor')f'which dual-function n51" switch vwill operate-in an idle manner so far as its cooperative" functioning by way-"Of extending tlier-"allj in the direction of the called subscriberis concerned; until the first twoil'igits of th e" called'f nulrfibeu'which incidentally index the suh-oi'fice and the sub-oflice division; have been sent; whereupon" the said switch seized by the primary-line switch will be automatically'converted into a switch hav in'gtl'le function's-of a-third selector. I

"#12. Incidental to"*th'e 'secondflig'it being called; ,Whoreupm'i the switch is converted in a selector.- asget -r n -a supplemental condition -s'e t up-whicl'1- bars the-:"switch from new e oinu'wtors in a specific thou sn -uls grol'ip and opens the way for selecting cr'mnectorsi in analternative thousands group. :"H'nrt is to say,'-thes\\7itch functioning as a selector-innsaccess tod'en hundied's groups oF connectors-in each-fol" tiv'o thousa-mls= gt-011px and further I that the second digit sent will not only-index, but will set tlw'switeli forselecting only in' the numerically correspondingthousands group of conmotors. The switch, due to its condition set-up incident to "receiving the seconddigit series, though its wipers have been restored to normal position," now involves a preselection of one of two thousands groups, so the next operation' of the switch-responsive to the third digit series will be to select the directed hundred-in the said pre-s e'lected thousands group. Upon the fourth and fifth I digits'beingset the' selected connector will function in the well known'manner'to effect the completion of the connection to the called subscriber. I Y v I b; Permanently related to the" dual ttunc tioning switch is a novel duplex" lines'witch which-functions in a secondary tha'nneriineh dent to the seizure of the former, whereupon it will automatically seize anidletrunkextending through a reciprocal-functioning switch-to an incoming first selector in the main-branch" =oflice' to which {the 's'ub oflice belongs; f So that upon the calling subscriber initiating the call from his station connected subordinate to the"sub=6fiice, his terminating lineswit'ch -(pri'rna-rifi will automatically functionand seize an idle dual-functioning switch andthe" seized dual-functioning switch will consequently capacitate' its permanently related duplex lineswitch=(s'econdary) so'it will automatically function to seize an idle outgoing trunk from the sub-oflice to its comprising main-branch office; where it terminates in an incoming first selector, the latter being now in readiness toreceive -the first series of impul-ses constitutingthefirst digit of the called number. The dual functionin'g switch is also I susceptible to the said series of-impulses con'stituting the first digit. That is to sayy the dual-functioningswitch located in the sub office and the firstsselect-or iii the; main-branch oflice terminating the automatically inter linked trunked connection trom the subscri'bers'station will coi'ncidently operate under directivecontrol'fof the calling-deviee atthe calling subscribers station in step by-step inann'en' 521;; 5 7221 The'saidineoming first selector'in the main bramih oifice lias-the' well known coop'erati ve relation nthemain-branclr-otfice,

witli the second selectors I so. th'atibyz-tlie 'calling subscriber calling digits comprising a telephone number reached through its mainbranch oflice, the call will be advanced in the direction of the called subscriber as in the well known condition wherein a subscriber whose line leads directly to a lineswitch in the main-branch oflice initiates a. call and automatically attains connection with a local first selector. However, under the condition of forwarding the call from the incoming first selector controlled by the sub-ofiice call ing subscriber, the dual-functioning switch in the sub-ofiice will rotate on its normal level (not stepping-up its shaft), and then release to normal position at the termination of the first digit series, provided the first digit is pertinent to the sub-office. It remains at rest in its rotated-in position, incapacitated against further operative movement or affecting condition of the connection being established, if the first digit sent is not pertinent to the sub-office, and there remains until the calling subscriber replaces his receiver. It is to be borne in mind that upon the calling subscriber sending the second digit, the second selector in the main-branch office will function in a normal manner in extending the connection in the direction of the third selectors, and attains connection with a third selector level corresponding to a thousands group indexed by the second digit sent. If the dual-functioning switch does not restore to normal position following the sending of the second digit and, therefore, remains at rest where stepped-in, the succeeding digits will progress the call in the direction of the called subscriber by way of the main-branch oflice because the call is not destined to a subscribers line in the sub-oflice.

63. Assuming that the first digit sent -is pertinent to the sub-office and, therefore, the dual-functioning switch will rotate-in and then release to normal resultant to the first digit being sent, and that the second digit of the called number is now sent and which is also pertinent to the sub-office, the dualfunctioning switch which operated in the manner as before will again release to normal position resultant to the second digit ing sent. Incidental to the second releasing of the dual-functioning switch to normal osition, it automatically prepares its circuits (which are partially prepared incident to the said first release) to control its moving elements as a third selector, and it also causes the trunk seized through the duplex lineswitch to be released and be again seizable from either the sub-ofiice end or the main-branch office end thereof. Upon the calling subscriber sending the third digit of the called number, which will be pertinent to a hundreds group of the thousands group in the sub-oflice indexed by the second digit. the dual-functioning switch (functioning as a selector) will step its wipersup into alignment with the bank level corresponding to the two groups of connectors (wherein one of the groups has access to the called line), where it will automatically rotate-in and seize an idle one of these specific hundreds connectors in the thousands group determined, incidentally by the second digit sent. Upon the calling subscriber annexing the last two digits of the called number, the seized connector of the hundreds group indexed by the third digit will function in the well known manner and connect to and signal upon the called line. Upon the called subscriber responding, the telephone circuit from the calling to the called subscriber will be established.

0. To provide a set or pair of novel lineswitches, operated as a unit, hereinbefore referred to as a duplex lineswitch, wherein an element 0 thereof will at all times start automatically functioning where necessary to be prepared to seize an idle trunk without first rotating. That is to say, to always rest its wipers on the bank contacts of an idle trunk and to automatically move ofi and seek an idle set of trunk bank contacts upon which to rest its wipers should the trunk become busy by reason of it being seized from some other oint. An element B of the duplex lineswitch is desi ed to operate preferentially over the sai element C when the leading-conductors are seized. That is to say,

the element B will be the only element that will seize the set of bank contacts of a trunk its wipers may be resting upon, it the trunk is idle, or that will automatically start its rotation seeking an idle trunk to seize, if the duplex lineswitch is seized. However, a function of the duplex lineswitch is that, after the B element thereof has started its automatic rotation hunting for an idle trunk (if its wipers were not resting upon an idle trunk) and has assed over a pre-determined number of trunks as busy, the C element of the duplex lineswitch will become operative, that is it will either seize the idle trunk the bank contacts of which its wipers are resting upon, or in case the trunk that its wipers were resting u n the bank contacts of which became busy fore it was operatively introduced, upon the B element aving passed over the re-determined number of busy trunks, wil also start a hunting operation so that under this condition both elements of the duplex lineswitch will seek or hunt for an idle trunk. The first element (B or C) to encounter an idle trunk will seize it and incidentally incapacitate its companion element. In instances in commercial operation the trunks accessible to the C element would be over-flow trunks, not seizable to the B elements of duplex lineswitches, but comprise an auxiliary or reserve group provided so as to insure they would not be used unless there was a shortage of idle trunks in the general group as indicated by'the fact that the B element has rotated over the pre-de'g termined number of trunks without finding an idle one. 3 a 4 1 02. A function of the duplex lineswitch is that of rendering its leading-in terminals non-seizable by applying'a false busy thereto during the period the C element may be automatically rotating, because the trunk that it may be normally resting upon has become busy, by reason of a switch commonly accessible to it (from either end thereof) havin seized it.

(1. i further function of theduplex lineswitch is that if all the trunks accessible to both elements thereof in common with other lineswiches become busy a condition is set-up whereby, when the C element (or elements of a plurality of duplex lineswitches) start rotating autmatically from the last idle trunk contacts, because of the trunk becoming busy, or that the B element is in the process of hunting wherein all trunks are busy, the rotating test wiper will encounter a bank contact that, due to the set-up condition, will cause the duplex lineswitch element concerned to seize and. therefore. stop rotating, and apply a specific tone indexing the condition to the calling subscriber.

e. To providea novel selector (herein termed a reciprocal-functioning switch) in the sub'ofl iceaterminating an inter-oflice trunk" for forwarding incoming trafiic through its wipers that also comprehends the use wherein it will reciprocally function as a trunk repeater when its related trunk is seized as an outgoing trunk to the mainbranch oflice. a e

e2; A further function of the selector re ferred to in the foregoing paragraph (which may also be termed a second-third selector of the sub-otlice) is that itwill select in one of two alternative thousand trunk groups lead-v ing to hundreds groups of connectors thereof, depending upon the numerical Value of the third digit-called in extendinga connection from a calling subscribers telephone in a 'm'ain-branch. oflice to a su'bscribers tele: phone in'thcsub-ofiice.

f. To provide a novel means in a li-neswit'ch whereby if the lineswitch continues to automatically rotate over busy trunks and that none accessible to it are found idle, a distinctivc'tone will be applied to the leadingin line, audible-to that callinglsubscriber, apprising him ofthe condition so that he will refrain from" atten'ipting to effect the calling furt'lner, knowing that there are no available trunks accessible to theilineswitch and will, therefore, replace his receiver and cause the lineswitch to stop hunting. Heretofore, under the stated condition, the, lineswitches would frequently rotate for a prolonged period while" a calling subscriber either-held'the' line or proceeded with the call operations which, of fectual.

In the accompanying drawings:

' Fig. 1 shows a general. layout of a tele-. phone exchange system as contemplated under' the present invention. The portion of thediagram within the left hand dotted squareis to be understood as belonging to the sub-ofiice. The portion withinthe upper righthand dotted square is to be understood that thetwo said main-branch office are-con nected for inter-switching between all the subscribers thereof under directive control of the subscribers of the entire exchange Fig. 2 shows the assembly ofthe various sheets of drawings forming the system indicated in Fig. 1.

Fig. 3 shows a subscribers telephone T9, leading into a lineswitch A of well known type, located in the sub-ofiice.

Fig. 4 shows a novel pair of inter-linked or companion lineswitch elements B and C,

hereinafter referred to as a duplex line switch. 1 a

Fig. 5 shows a novel dualfunctioning switch D located in the sub-office which will function to divert a call in the direction of the called subscriber 'in the sub-ofiice.

Fig. 6 shows a novel combination incoming first selector and outgoing trunk repeater ll hereinafter referred to as a. reciprocal-functioning switclnlandis located in the sub office. v

Fig. 7 shows a subscribers telephone T7 accessible to a connector G. and a subscribers telephone T7 accessible to connector F. It also shows said connector F as having access to subscribers telephone T2; all in relation tothe sub-oiiice of the 2 main-brauch ofiice. Fig.8 shows armatures on four rehl vs of four respective switches Oftl' group that'are companion to and similar-to E. and are located in the sub-ofiicc of the 2 main-branch oflice. I

Fig.9 shows a novel iii-coming first selector H in the 2nulin-bra'nch oflicc. termi nating atrunk from the suh-oflice. The selector H- from the right of" the armatures of the leftrelay is the same as selectors which are welllmown.

Fig. 10 shows 'a noyel outgoing trunk repeater interlinked with selector'l-l and located in the 2 main ln'aneh office and the trunk extending therefrom to the switch I) in the sub-oflicc; y

' Fig. 11 shows a local second selector .l ('uoperatingwith T incomingfirst selector '11, a

course, would' be inef third selector K cooperating with a second selector J and a connector L cooperating with a third selector K, a subscribers telephone T11 in the 2 main-branch otfice accessible to the connector L, and a novel lineswitch M associated with the line leading to the said telephone T11, together with a first selector 0 accessible to the lineswitch M, a local second selector N, accessible to first selector O and a trunk extending from two of the levels of second selector N to the trunk leading to E by way of repeater I.

Fig. 12 shows a subscribers telephone T12 in the 3 main-branch ofiice leading into a lineswitch R of well known type. The lineswitch R has access to first selector Q, and first selector Q has access to second selector P. The subscribers telephone T12 reached through the 3 main-branch ofiice is accessibe to incoming first selector H in the 2 main-branch office by way of second selector S, third selector T and connector U.

By way offurther explanation, selectors, regardless of their denomination, O, N, J, K, Q, P, S, S and T may be assumed similar in detail to the portion of selector H in Fig. 9 from the right of the left relay thereof. Also, connectors G, L and U may be assumed similar in detail to connector F in Fig. 7, which latter is a well known type of connector.

Referring to certain of the figures:

The subscribers telephones T2, T7, T7, T11 and T12 are of the usual series type of automatic telephone having a calling device of the general class as shown in British patent to Dicker, No. 29,654 of 1910.

The lineswitches A and R are of the general class as shown in U. S. patent to Lamb, No. 1,193,160 granted Aug. 1, 1916, and are well known. The lineswitch M belongs to the same class as lineswitches A and R with a novel modification thereto to operate in accordance with, and to embody the present invention.

The first selectors H, O, and Q; the second selectors N, P, S and S and the third selectors T and K are all of the general class as shown in U. S. patent to Keith and Erickson No. 815,321 granted March 13, 1906, of course, modified in mechanical and circuit details to operate on the well known socalled two-wire principle. It is to be understood that a selector, such as E in U. S. patent No. 13,901 reissued to Frank Newforth April 13, 1915, may be substituted for said H (from'the ri ht of the armatures of the left relay thereof O, Q, N, P, S, S, J, T

and K throughout the description and for the purposes contemplated under the present invention.

The connectors F, G, L and U are of the general class as shown in U. S. patent to Keith and Erickson No. 815,176, granted March 13, 1906, of course, modified in mechanical and circuit details to operate on the well known so-called two-wire principle. It is to be understood that a connector, such as H, in U. S. patent No. 13,901 reissued to Frank Newforth April 13, 1915, may be substituted for said F, G, L and U throughout the description and for the purposes contemplated under the present invention.

The duplex lineswitch, made up of the companion elements C and B, the said elements are each of the same general class as lineswitch A, modified of course, to operate in accordance with, and to embody the present invention.

The dual-functioning switch D and the reciprocal-functioning switch E are of the same general class as selector H (not considering the relay on the extreme left thereof added in embodying the present invention). The switches D and E are, of course, modified in mechanical and electrical details from the referred to switch H to operate in accordance with and to embody the present invention:

It, of course, is understood that in applying the present invention to a commercial system the various elements shown as oooperating with bank contact sets would be installed in plurality depending-upon the capacity of the system. Also, that more than one switch would have access to the same lines and trunks through companion bank contacts that are in corresponding multiple relation with the companion bank contacts ofother switches. In order not to unduly involve the drawings and descriptions the said multiple connections have not been completely detailed, though they are indicated in some instances by extended lines. For example, there would be a plurality of subscribers lines, such as is shown leading from T2, terminating in the lineswitch A. Then, a group of lineswitches, such as A, would have common access to a plurality of trunks, each leading to a dual-functioning switch D and its companion secondary duplex lineswitch shown in Fig. 4 as elements B and C. A group of duplex lineswitches (such as com-' panion elements B and C), would have common access to a plurality of trunks each leading to a. reciprocal-functioning switch as E and to an incoming first selector in the 2 main-branch oflice. It will be borne in mind in this connection that the companion duplex lineswitch elements B and C may each have access to individual groups of reciprocalfunctionin switches such asE and trunks leading to lncoming first selectors therefrom respectively as stated, or that both said elements B and C may have access to a single said group commonly, as is shown in the drawings.

To simplify the drawings and descriptions, battery and ground are shown as independent sources throughout, wherever applied,

but it is to be understood that the system is of the common battery type. In the descriptions, when a circuit is traced to a winding, the opposite terminal of which .is shown applied to grounded battery or to ground, t e described circuit is to be considered as traced to ound through the winding to battery, or irect to ground as indicate The rformance of the equipment will be detailed under difierent assumed operative,

conditions, bearing in mind the equipment elements may be further variously organized in the assembly of a system.

Referring to the accompan 'ng drawings:

Assuming a call is made om telephone T2 to tele hone T7, the respective calling numbers 0 whichare 22211 and 21211 Upon the calling subscriber at telephone T2 removin the receiver from the switchhook to initlate the call, a circuit will be established from the winding of slow-releasing relay 301, armature 302, line conductor 303, telephone T2, line conductor 304, armature 305, to the grounded resting contact thereof, relay 301 actuating. It will be assumed that the wipers 306 to 308 (inclusive) are resting on the bank contacts 309 to 311 respectively, of an idle trunk and that, therefore, the bank contact 309 does not constitute ground poten-- tial, as willappear presently. Upon relay 301 actuating, a circuit will be established from winding of motor magnet M3, armature 312, conductor 313, winding of cut-oflt' relay 314, conductor 315 to grounded armature 316. Relay 314 will actuate over this energized circuit but the current will not be of suflicient strength to operatively energize motor-magnet M3 because of the inclusion of the winding of relay 314. Upon the actuation of-relay 314, ground from armature 316, conductor 315, contact 317 will be applied, through armature 318 to private wiper 306, bank contact 309, conductor 319 to armature 501 in switch D. A circuit can also be traced from upper winding of relay 502 of switch D, armature 503, conductor 504, bank contact 310, wiper 307, armature 302 over the described path, including telephone T2, conductor 304, armature 305, wiper 308, bank contact 311, conductor 320, armature 505, to lower winding of relay 502, relay 502 actuating. A circuit can now be traced from grounded armature 506, to the winding of slow-releasing relay 507, relay 507 actuating. Armature 501 is now in engagement with grounded con tact 508 and contact 509, thus armature 501 has supplemental ground applied to it before relay 301 retracts its period after the attraction of armatures 302. and 318, so that there is no lapse of ground potential on conductor 319 nor conductor 315, relay 314 being now maintained from ground received over conductor 319 from grounded contact 508.

Ground from contact 508 is applied through armature 501, conductor 319, armature 512, conductor 513, to thewinding of rela 401, the latter relay. actuating. Slowre easing relay 402 will coincidently actuate as will appear presently. It will be assumed that wipers 403 to 406 of element B are resting on the bank contacts 407 to 410, res tivel of an idle trunk and that, there ore, the ank contact 407 does not constitute ground potential, as will appear presently. An operative circuit can be traced from grounded conductor 319, conductor 418, armature 411, armature 412, armature 413 to the winding of relay 402. Upon relay 402 actuating, a circuit will be established from the winding of motor ma net M4, armature 414, conductor 413 windmg of relay 416, armature 417, to conductor 418 which leads to grounded conductor 319. Relay 416 will actuate over this energized circuit, but the current will not be of sufiicient stren th to operatively energize motor magnet 4 because of the inclusion of the winding of relay 416. A circuit can now be traced from grounded conductor 418, armature 420,

armature 422, wiper 404, bank contact 408,

conductor 423, conductor 424, to the winding of slow-releasing relay 601, the latter relay actuating. A circuit can also be traced from grounded conductor 418, through armature 420, wiper 403, bank contact 407, conductor 426, conductor 427, to armature 602. A circuit can also be traced from upper winding of relay 603, make-before-break spring 604, upper winding of relay 605, armature 606, armature 607, con-ductor 608, makebefore-break spring 609, conductor 428, conductor 429, bank contact 409, wiper 405, armature 430, conductor 431, conductor 504, bank contact 310, wiper 307 over the described path including telephone T2, wiper 308, bank contact 311, conductor 320, conductor 322, contact 433, wiper 406, bank contact 410, conductor 434, conductor 435, make-before-break spring 610, conductor 612, armature 613, armature 614, lower winding of relay 605, made-before-break spring 615 to lower winding of relay 603, relay 605 actuating. The windings of relay 603 are so disposed that the current traced through them neutralize each other, and therefore, no tractive effort is exerted upon its armatures. The object of relay 603 will appear presently.

Relay 605, being new actuated, a circuit can be traced from itsgrounded armature 616 to the winding of slow-releasing relay 617, causing it to actuate. A supplemental ground is applied to conductor 418 from contact 618, armature 602 conductor 427 conductor 426, bank contact 407, wiper 403, armature420, to conductor 418. This supplemental ground will prevent a lapse of ground potential occurring to conductor 319when armature 501' retracts, as will appear presently. So relay 416 is maintained actuated, dependent on armature 602. Also that the traced ground path from wiper 404 to conductor 418 is dependent upon the attracted condition of armature 602. At this juncture, relays 314, 3 502, 507, 401, 416, 601, 605 and 617 are actuated.

It was hereinbefore described that relay 502 was maintained actuated over a circu1t path including conductor 504, telephone T2 and conductor 320. It is, therefore, manifest that both relays 605 and 502 are maintained attracted directly dependent upon the circuit being maintained through the telephone T2. A circuit can now be traced from lower winding of relay 801, armature 802, armature 15 804, conductor 805, armature 620, conductor 621, armature 622, outside winding of electro-polarized relay 624, conductor 626, armature 627, conductor 628, conductor 629, armature 806, armature 808, upper windingof re- 90 lay 801, relay 801 actuating. A c1rc'u1t can now be traced from grounded armature 809, to the winding of slow-releasing relay 810, relay 810 actuating. Before detailing the assumed call from calling tele hone T2 to called telephone T7 attention is directed to the fact that dual-functloning switch D (andcompanion switches of its group), and reciprocal functioning switch E (and companion switches of its group), have common access to two one-thousand groups of connectors. The wipers of said D are designed to co-operate with eleven levels of bank contacts. The first or lower-most level ali s with the normal position of the wipers an has a novel purpose, as will appear. The ten levels of bank contacts above the said lower-most level are attained by the wipers stepping a corresponding number of vertical steps into alignment therewith, and then automatically rotating-in until a set of bank contacts of an idle trunk is engaged by the set of wipers, when they will be seized. There will usually be ten sets of bank contacts in each level. It follows that since D is the first numerical switch relating to the sub-oflice, that the position of the levels thereof index the hundreds group of connectors to which they lead. That is to say, there will be as many hundreds grou s of connectors accessible (being ten oneundred groups, numbering from one to naught) as there are levels above the normal level. However, a novel provision in the dual-functioning switch D enables alternative corresponding hundred groups in two one-thousand groups to be automatically selected, depending upon a set-up condition introduced incidental to converting the said D into a selector, as will appear presently. Suflice it to say, at this time, that 60 the switch D functioning as a selector has direct access to two one-thousand connector groups, and therefore, to two thousand subscribers lines. It will also appear presently, that these two thousand subscribers lines have numbers belonging to the 2 mainbranch oflice, but which, of course, are segregated into the sub-office. It will appear presently that these two thousands and 2 thousands of the 2 main-branch oflice. The telephone T2, as indexed by its telephone number 22211, belongs to the 2 thousand of the 2 main-branch oifice, or in other words, it belongs to the 22 thousand of the exchange system, and that calling 22 (as the first and second digits of a telephone number) from any subscribers telephone in the said sub-ofiice of the exchange system will cause the extension of this calling subscribers line to be reverted to the sub-exchange of the 2 main-branch ofiice containing the said two one-thousand groups of subscribers lines, and that the switch D then terminating the connection from the calling subscribers telephone inthe sub-ofiice has a set-up condition adapting it to select numbers in the 22 thousand group, barred against selectin numbers in the 21 thousand group thereo Attention is also directed to the fact that the wipiers of the reciprocal-functioning switch (and companion switches of its group), is designed to co-operate with ten levels of bank contacts. The said ten levels are attained b the wipers stepping a corresponding number of vertical steps into alignment therewith, and then automatically rotating-in until a set of bank contacts of an idle trunk is engaged by the set of wipers, when they will be seized. There will usually be ten sets of bank contacts in each level. It follows, that since E is the first numerical switch relating to incoming calls to the suboflice, that the position of the levels thereof index the hundred group of connectors to which they lead. That is to say, there will be as many hundreds groups of connectors accessible (beingten one-hundred groups, numbering from one to naught) as there are levels above the normal position of the wipers. However, a novel provision in the reciprocalfunctioning switch E enables alternative corresponding hundred groups in two onethousand groups to be automatically selected are the 1 through its ten levels, depending upon a set- I up condition introduced incidental to seizing the said E through the dual-functioning repeater I, as will appear presently. Suifice it to say, at this time, that the switch D has direct access to two one-thousand connector groups, and therefore, to the two thousand subscribers lines.

In order not to unduly involve the drawings, a single level, such as lead to connectors, is shown as cooperating with each said D and E respectively. This is the second level, reached and rotated-in upon automatically consequent to the wipers of said D and E respectively being stepped into alignment therewith. The telephonic and private bank contacts of the corresponding levels of the said D and E (and their respective companion switches) are in multiple relation. Bearing in mind that in commercial installations there would ordinarily be ten sets of bank contacts tothe level, only the first and third sets of line and private bank contacts of the said second level with respect to the bank contacts of switches D and E are shown as connected in multiple relation, respectivel It will appear presently that the said rst sets of multipled common bank contacts lead to a connector F, and that the said third sets of multipled common bank contacts lead to connector G. It will also appear presently that the said connector F belongs to the 22 thousand group in the sub-oflice and that the said connector G belon to the 21 thousand group in the sub-o ce. It will further appear presently that which connector F or is seized, by either said D or IE, will depend upon the numerical value of the digit sent next precedin the one sent to complete the connection to the connector seized.

Referring again to the bank contact sets cooperative with the dual functioning switch D and the reciprocal-functioning switch E, it will be noted that the second set of blank contacts respectively are similarly related to the respective switches as is the first set, and therefore, adapted to be terminals of a connector of the same group as contains connector F wherein connector F is the first choice. In a like manner the fourth set of bank contacts respectively are similarly related to the respective switches as is the third set, and, therefore, adapted to be terminals of a connector of the same group as contains connector G wherein connector G is the first choice. Bearing in mind that the levels of bank contacts of D and E would ordinarily have ten or more rotary positions and ban terminals corresponding therewith, it will be manifest that the groups containin connectors F and G may be enlarged so t at they will contain five or more connectors each, though the respective groups do not necessarily have to contain an equal number of connectors. The number of connectors in each group would be governed by the traffic reuirements. It is manifest then also, that the rst five bank contact sets may lead to a group of connectors containing connector G, for example. It will appear that the exampled disposition of the bank contacts last set forth can be modified widely, for example, the first and alternate bank contact sets may leadto connectors of a group containing connector F and the second and'alternate bank contact sets may lead to connectors of a group containing connector G.

Returning now to the condition automaticall set up consequent to the callin subscri r at telephone T2 removing the receiver. In View of the foregoing description a telephonic circuit has been extended from telephone T2 to armatures 804 and 806 and to armatures 503 and 505. Relays 314, 502, 507, 401,416, 001, 005, 617,801 and 810 are nowactuated. Due to conductor 319 bein grounded, the trunk seized by lineswitch 1% will be guarded against intrusion by other lineswitches of the grou containing said A. Due to conductor 426 eing grounded the trunk leading to switch 11 seized by duplex lineswitch element B will be guarded against intrusion by other duplex lineswitch elements of the group containing the switch comprised of elements B and C. Due to conductor 315 being ounded, the line leading to telephone T2 wil be guarded against selzure by connector F and other connectors of the group containing connector F. Relay 810 being actuated, a circuit can be traced from its G grounded contacts 812, conductor 813 to the rst bank of contacts 16 and 17 of the first and second levels of second selector N and over conductor 18 to the first bank contacts 19 and 20 of the first and second level of second selector P. Contacts 16, 17, 19, and 20 are private bank contacts of the 2 mainbranch office end of the trunk out-going from reciprocal-functioning switch E, so that the said trunk is guarded against intrusion from the 2 main-branch oflice end consequent to the trunk being seized by the automatic operations initiated by the calling subscriber at telephone T2 removing the receiver.

Upon the calling subscriber manipulating the calling device 322 in accordance with the first digit 2 of the called number, causing two open impulses to the traced path including telephone T2, relays 605, 801, and 502 will de-actuate and re-actuate two times responsive thereto. Referring first to switch D, when grounded armature 506 retracts, a circuit can be traced from said armature, armature 515, armature 516, winding of slow-releasing relay 517, armature 518, conductor 520 to the winding of the rotary magnet R5, causing the said rotary magnet to operate and advance wipers 521 to 524 two rotary positions so that wiper 522 will stop, resting upon bank contact 525. The bank contacts on this level (bearing in mind that 'the shaft has not been stepped vertically),

engageableto wipers 521, 523 and 524 respectively, are unconnected and, therefore, have no operative purpose. Relay 517 is caused to actuate consequent to the circuit including its winding being closed, and upon its deactuation its period after the last closed impulse, a circuit will be established from grounded contact 508, armature 501, contact 509, conductor 510, armature 526, upper winding of relay 527, conductor 528, arm ature 529, conductor 530, wiper 522, bank contact 525, conductor 531, make-before-break spring 532 to upper winding of relay 533, relays 533 and 527 actuating. A locking circuit for relay 527 can be traced from its lower winding, armature 534, conductor 535,

armature 536, conductor 510 to grounded contact 508.

In this connection, the set of springs designated RON are rotary off-normal springs which operate consequent to the first rotary movement of the shaft carrying wipers 521 to 524 and the set of springs designated 0 5 are vertical off-normal springs which operate consequent to the first vertical movement of the said shaft.

A circuit can now be traced from grounded contact 508. armature 501 conductor 510, armature 537, armature 538, conductor 539, spring 540, to the winding of release magnet R65, causing the said release'magnet to actuate and restore the shaft to normal position,

In this connection, it may be noted that shunted relay 541 is caused to actuate (but as will appear, to no operative purpose, due to spring set 0N5 being normal) consequent to the attraction of armature 537, by reason of the spring set RON operating coincident with relay 517 and rotary magnet R5 actuating. A locking circuitfor relay 533 is established consequent to its actuation from its lower winding armature 542, conductor 543, armature 544, conductor 510, contact 509 to grounded contact 508. At this juncture relays 502, 507, 527, and 533 of switch D are actuated and its shaft is at normal position.

Referring to switch E, when grounded armature 616 retracts a circuit can be traced from said armature 616, armature 630, armature 631, conductor 632, armature 633 to the winding of slow-releasing relay 634, relay 634 thus actuating and remaining so until its period after the last impulse is sent, when it will de-actuate. While relay 634 is actuated, its armature 635 serves to apply a short circuit between conductor 626, and armature 622 thus augmenting the current traversing the traced circuit including the windings of relay 801. Armature 627 retracting two times opens the traced circuit including the windings of relay 801 correspondingly, causing relay 801 to de-actuate and re-actuate two times coincident thereto. Upon the de-actuation of relay 634 following the sending of the two impulses from calling device 322, the short circuit placed upon the outside winding of relay 624 will be removed so that this winding will be again included in the traced circuit including the windings of relay 801.

At the time relay 601 actuated a circuit is established from grounded contact 618, armature 602, conductor 427, armature 637 to the inner winding of relay 624. The current traversing the inner winding of relay 624 is not of suflicient strength to operatively attract its armature 639. It will be borne in mind that the outer winding of relay 624 is included in the traced path including the windings of relay 801. However, the direction of current is opposite to that traversing the inner winding and is of such strength that the core will not operativelyattract a1- mature 639. It will presently appear that upon a response being attained from the called telephone that the current traversing the outer winding of relay 624 Will be reversed in direction consequent to the response. Under this condition of both windings energizing cumulatively the armature 639 will be operatively attracted for objects as will appear presently.

Upon relay 801 de-actuating two times, as referred to, a circuit is established from grounded armature 809, armature 815, armature 816, winding of slow releasing relay 817 to the winding of vertical magnet V9, causing it to step the shaft carrying wipers 818 to 820 two vertical steps into alignment with the second level of cooperating bank contacts, and there automatically rotate-in and seize the first set of bank contacts leading to a selector of a disengaged trunk, which in this case will be assumed as the first set 821 to 823. The operation of H, as to its automatic rotatin -1n and seizing function, is well known. elay 824 will actuate to effect the seizure so that the telephonic circuit will be extended from conductor 629 and 805 as follows from conductor 629, armature 806, armature 808, conductor 824, wiper 819, bank contact 822, conductor 825 to the upper winding of a relay in second selector J correspondin to relay 801 of selector H. Conductor 805 1s continued to armature 804, armature 802, conductor 826, wiper 820, bank contact 823, conductor 827 to the lower winding of the said relay in selector J corresponding to said relay 801, the said latter relay actuating and preparing the circuits of the selector J to receive the impulse constituting the second digit 1 about to be sent. Remembering the condition of switch D last described, at this juncture relays 601, 605 and 617 of switch E are actuated and relay 824 of selector H is actuated. Also, relays in sclector J corresponding to relays 801 and 810 of selector H. Relay 824 is held actuated in the well known manner due to receiving ground over conductor 828 (corresponding to conductor 813), bank contact 821, wiper 818, conductor 829, armature 830, conductor 831, armature 832, conductor 833, spring 834, winding of shunted relay 835, to grounded battery. However, the current traversing the traced path not being of sufiicient strength to operatively afiect relay 835, though its included relay 824 will be operatively affected.

Upon the calling subscriber manipulating his calling device 322 in accordance with the second digit 1 of the called number, causing one open impulse to be applied to the traced path including telephone T2, relays 605 and 502 and also the relay in second selector J corresponding to relay 801, whereupon they will de-actuate and re-actuate one time responsive thereto. Referring first to switch ed contact 508, armature I), when grounded armature 506 retracts, a circuit can be traced from said armature, armature 515, armature 516, winding of relay 517, armature 518, conductor 520, to the winding of rotary magnet R5 causing the said rotary magnet to operate and advance wipers 521 to 524 one rotary position so that wiper 522 will stop, resting u on bank contacts 547. Relay 517 is cause to act in the manner as before described and unlock the described circuit including the lower winding of relay 527, whereupon relay 527 will de-actuate. Upon the de-actuation of relay 517 following the impulse to the rotary magnet a circuit will be established from ounded contact 508, armature 501, contact 509, conductor 510, armature 526, upper winding of relay 527, conductor 528, armature 529, conductor 530, wiper 522, bank contact 547, conductor 548, armature-549 to the upper winding of relay 550, causing said 550 (and said 527) to actuate and lock its lower winding through armature 553, conductor 510, contact 509, armature 501, to grounded contact 508. Relay 527 will be re-locked over the before described locking path. A pathcan also be traced from grounded contact 508 over the described path includlng armature 549 off-normal spring 551 to the winding of slow-actuating relay 552, causing said relay 552 to actuate and look its winding through armature 526 to grounded conductor 510.

A circuit can now be traced from ground- 501, conductor 510, armature 537, armature 538, conductor 539, spring 540 to winding of the release magnet R05, causing the said release magnet to actuate and restore the shaft to normal position. At this juncture relays 502, 507, 527, 552, and 550 of the switch D are actuated, and the shaft is at normal position.

Referring to switch E, when grounded armature 616 retracts the one time responsive to the calling device 322, the same functioning in switch E will take place as before described when the first digit 2 was sent so that its functioning at this time will not be detailed. However, the selector J now controlled by armature 627, will be caused to function by stepping its shaft one vertical step into alignment with the first bank level thereof and automatically rotate-in and seize a set of dead bank contacts corresponding to a selector of the 1 thousand group of (second) selectors in the 2 main-branch office. However, inasmuch as the call is destined to a telephone in the sub-oflice and there is no 21 thousand in the main-branch office there is no particular interest in its operative effect upon switches in the 2 main-branch oflice, for it will appear presently that the trunk leading to the first selector H will be released incidental to sending of said digit 1.

In View of the previous description it is clear that coincident to selector J seizing in the manner set forth. relay 550 actuated and locked. Consequent to relay 550 actuating the circuit previously traced to the winding of relay 401 is opened by armature 512, causing it to dc-actuate and open the traced path through the winding of relay 416, in turn causing the latter relay to de-actuate and disassociatc conductors 431 and 322 at armature 430 and contact 433 respectively, and also nnground wipers 403 and 404 due to the retraction of arinaturcs 420 and 422 respectively. Relay 601 will retract its period after armature 422 retracts. This will open the traced energizing circuit of relay 605 and the latters dependent relay 617 in turn, whereupon the ground existing on conductor 427 will be disconnected, rendering switch E normal and its leading-in conductors free and seizable as in the manner hereinbefore set forth. Incidental to relay 605 de-actuating and its armature 627 retracting the described energizing circuit including conductors 629 and 805 will be opened, and the dependent switches H, J, and K will 1e l()l(- to normal, and the busy ground Will be removed from conductor 813 and its attachments. Thus, the trunk is again seizable to selectors N and P and to duplex lineswitches of the group containing B and C.

Bank contacts 554 and 555 are in multiple relation, tied to conductor 556, which is local to switch D. Therefore, ground potential is applied from conductor 510 through armature 557 to conductor 556 and to bank contacts 554 and 555. These latter bank contacts are engageable by wiper 521, which latter is tied electrically to private wiper 522. It is thus manifest that if wipers 523 and 524 are caused to engage bank contacts 558 and i 559 or 560 and 561 respectively, regardless of whether private bank contacts 562 and 563 constitute ground potential, conductor 530 will receive ground from wiper 521. That is to say, that there is a false busy condition guarding line bank contacts 558 and 559, and 560 and 561 respectively against seizure under any conditions under the set-up condition now existing in the switch D, and therefore, connector F and its companion connectors of the group of connectors accessible to the two-hundred group of the 22 thousands group of subscribers lines are barred against seizure. However, the bank contacts 564, and 555 engageable by wiper 521 do not constitute ground potential due to conductor 566, which is local to switch D, attached thereto being free of armature 557. Under this condition bank contacts 567 and 568, and 569 and 570 respectively will be seizable, wholly dependent upon whether private bank contacts 571 and 572 do not constitute ground potential respectively, which, as will appear, only ensues when the trunks leading from the said sets of contacts are disenga ed. Connector G bein assumed to be ngaged bank contact 5 1 will not constitute ground potential. It will be noted that connector G has access to the called line leading to the telephone T7, which it will be recalled is in the 21 thousands group of subscribers lines. 7

Referring again to connectors F and G it will be manifest that since they are reached through the second levels of the switches D and E that they are each of the 2 hundreds group of the said 2 thousands and the said 1 thousands groups in the sub-ofiice, respectively. That is to say, connector F has access to the 2 hundred group of the 22 thousands group of the exchange and that the connector G has access to the 2 hundred group of the 21 thousands group of the exchange.

It will be remembered here, that the second di 't called by the calling subscriber was and in view of the fact the next, or third digit that he will send is 2, and that the switch D will be responsive thereto, functioning as a selector, it will cause its wipers 521 to 524 to automatically hunt on the second level of bank contact accessible to it, wherein the only connector not barred, by reason of the position of armature 557 is connector G belon 'ng to the 21 thousands group of subscri ers. As will appear presently, the second digit sent by the calling subscriber not only releases the trunk leading to the 2 main-branch ofiice, but sets-up a condition in the switch D that constrains it to select connector G accessible to the 21 thousands group of subscribers lines. Of course, it is understood that there are a plurality of connectors such as G and F in their respective groups successively seizable, depending upon their busy or idle condition, with relation to other switches having common access to them, as has been referred to heretofore, so in the subsequent descriptions reference will be made to the individual switches F and G as re resentative of their respective groups.

pon the calling subscriber at telephone T2 manipulating the calling device 322 in accordance with the third digit 2, relay 502 will de-actuate and re-actuate two times responsive thereto, whereupon a circuit can be traced from grounded armature 506, armature 515, armature 516, winding of relay 517, armature 518 to the winding of the vertical magnet V5, causing it to operate two times and step the shaft carrying wipers 521 to 524 into alignmentwith the second level of bank contacts.

At the time the vertical magnet V5 steps the shaft from its normal position and the contact springs 0N5 operate, a'circuit can be traced from grounded conductor 510, armature537,

spring 574, to the winding of shunted relay' 541, relay 541 actuating. A locking circuit for relay 541 can be traced from grounded off-normal 8 ring 575, armature 576, armature 577 on the rotary magnet R5, spring 574 to its winding,and it will be borne in mind this can only exist when the ofi-normal s rings ON 5 are operated. When relay 517 e-actuates its period after the last impulse to the vertical magnet V5, a circuit can be traced from grounded conductor 510, armature 537, armature 579, spring 580 to the winding of rotary magnet R5, causing it to actuate and advance wipers 521 to 524 into engagement with bank contacts 554, 562, 558 and 559 respectively. Bearing in mind that bank contact 554 constitutes ground potential, received through armature 557, this ground will be conducted to wiper 521, conductor 530,

' armature 529, conductor 528, spring 581,-conductor 582, armature 583, conductor 584, armature 577, spring 57 4 to the winding of relay 541, causing it to re-actuate, its previously described locking circuit having been broken incidental to armature 577 on the rotary magnet "R5 attracting incidental to it driving the shaft the first rotary step. Relay 541 being actuated a circuit path can again be traced from conductor 510, armature 537, armature 579, spring 580 to the winding of rotary magnet R5, causing it to re-actuate and drive the wipers 521 to 524 into engagement with bank contacts 555, 563, 560 and 561 respectively. Armature 577 attracting as before, incident to the operation of the rotary magnet R5, opens the hereinbefore described locking circuit for relay 541, whereupon due to wiper 521 finding ground on bank contact 555, received through armature 557, relay 541 is again caused to actuate in the manner before described when wiper 521 encountered ground on bank contact 554, whereupon rotary magnet R5 is again energized to drive wipers 521 to 524 into engagement with bank contact 564, 571, 567 and 568 respectively. Connector G being assumed to being disengaged, and therefore, bank contact 571 does not constitute ground potential, and the further fact that bank contact 564 does not receive ground over conductor 566 due to it being free of armature 557, the wiper 522, nor its companion wiper 521 does not apply ground potential to conductor 530 to cause relay 541 to reattract. Also, conductor 584 does not now constitute ground potential as received from grounded spring 575 or over conductor 530 from one of wipers 521 or 522. Ground potential is removed from the upper winding terminal of relay 585, so that a circuit can now be traced from grounded conductor 319, winding of slow-actuating relay 585, conductor spring 574, to the winding relay 541, which is in series relation to the Q winding of relay 585, is not energized sufliciently on said 541.

to operatively attract the armatures 

